This invention relates to heat transfer recording, where a desired letter or an image or both is to be recorded on a recording sheet by heating, and more particularly to a heat transfer printer and a heat transfer process capable of recording on an ordinary, versatile sheet of paper a heat-sublimable or vaporizable dye without using any specific recording sheet, and to a heat transfer ink sheet.
The heat transfer ink sheet so far used in the heat transfer printers is such a heat transfer ink sheet that a dye is fixed on a substrate sheet by a binder as an ink layer, where recording is carried out by heating the heat transfer ink sheet, as laid on a recording sheet, by a heating means, thereby selectively transferring the dye as a sublimable or vaporizable dye or a meltable ink in the ink layer onto the recording sheet in accordance with a letter or an image or both. However, in the case of the meltable ink, it is hard to obtain a tonal graduation. In recording a full color image having a tonal graduation, generally an ink sheet containing a sublimable or vaporizable dye is widely used.
One example each of a conventional heat transfer printer and a heat transfer ink sheet will be described below according to the disclosure of Japanese Patent Application Kokai (Laid-open) No. 57-169370. A heat transfer ink sheet comprises a substrate sheet and an ink layer laid thereon. The substrate sheet (base film) is composed of polyethylene terephthalate, etc., and the ink layer is a layer comprising a sublimable or vaporizable dye fixed by a binder resin, etc. A heat transfer printer comprises a platen rubber roller and a thermal head. The heat transfer ink sheet is laid on a recording sheet so that the ink layer of the ink sheet may be in contact with the recording sheet, and passed between the platen rubber roller and the thermal head under a pressing load. At the same time, the contact part is heated by the thermal head, while controlling the heating temperature and the heating time, thereby transferring the dye to the recording sheet from the ink layer. The recording sheet for use in the heat transfer is limited, and a specific sheet is used. That is, a polyester sheet, a polyester-treated sheet, a cross-linked polyester-treated sheet, a sheet treated with a mixture of polyester with polyvinylpyrrolidone, etc. have been used as the recording sheet. In other words, a specific sheet comprising a sheet and a polyester-based resin, etc. readily dyeable with a sublimable or vaporizable dye, as applied thereto, has been used as such a recording sheet.
When the commercially available, ordinary, versatile sheet is used as recording paper in place of a specific recording sheet together with a heat transfer ink sheet comprising a sublimable or vaporizable dye, the letter or image or both transferred onto the recording paper by the sublimable or vaporizable dye from the heat transfer ink sheet has such problems as being weak and less discriminate, and has poor recording preservability. A specific recording sheet has no such problems, but is expensive and is not easily available owing to the limited versatility.